U.S. patent application number 12/087394 was filed with the patent office on 2009-03-12 for microreactor glass diaphragm sensors.
This patent application is currently assigned to CORNING INCORPORATED. Invention is credited to Jerome Vivien Davidovits, James Scott Sutherland.
Application Number | 20090064790 12/087394 |
Document ID | / |
Family ID | 38228807 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090064790 |
Kind Code |
A1 |
Davidovits; Jerome Vivien ;
et al. |
March 12, 2009 |
Microreactor Glass Diaphragm Sensors
Abstract
Microfluidic devices having wall structures comprised of
sintered glass frit and further including a glass, glass-ceramic or
ceramic membrane structure sealed by a sintered seal to said wall
structures, such that a fluid passage or chamber is defined at
least in part by the wall structures and said membrane structure.
This allows for changes in pressure within the fluid passage or
chamber to cause deflections of the membrane structure, providing
for direct measurement of pressure within the device. The
microfluidic device may have both floors and walls of sintered
frit, or may have only walls of sintered frit, with planar
floor-like substrate structures, thicker than the membrane
structure defining the vertical boundaries of the internal
passages. The device may include multiple fluid passages or
chambers each defined at least in part by a membrane structure.
Multiple membrane structures may be used in a single device, and
one single membrane structure may be used for multiple passages or
chamber.
Inventors: |
Davidovits; Jerome Vivien;
(Thomery, FR) ; Sutherland; James Scott; (Corning,
NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Assignee: |
CORNING INCORPORATED
Corning
NY
|
Family ID: |
38228807 |
Appl. No.: |
12/087394 |
Filed: |
December 22, 2006 |
PCT Filed: |
December 22, 2006 |
PCT NO: |
PCT/US2006/049251 |
371 Date: |
June 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60755601 |
Dec 31, 2005 |
|
|
|
Current U.S.
Class: |
73/718 ;
257/E21.001; 438/53; 73/720 |
Current CPC
Class: |
B01J 2219/00963
20130101; B01J 2219/00783 20130101; B81B 2201/051 20130101; B01J
2219/00907 20130101; B01J 2219/0086 20130101; C03C 2218/328
20130101; B01J 2219/0097 20130101; B01J 2219/00853 20130101; B01J
2219/00831 20130101; C03C 2218/33 20130101; B81C 2201/019 20130101;
B01J 2219/00824 20130101; B81B 2203/0127 20130101; B81B 7/02
20130101; B01J 19/0093 20130101; B81B 2201/0264 20130101; C03C
17/04 20130101 |
Class at
Publication: |
73/718 ; 73/720;
438/53; 257/E21.001 |
International
Class: |
G01L 9/12 20060101
G01L009/12; G01L 9/04 20060101 G01L009/04; H01L 21/00 20060101
H01L021/00 |
Claims
1. A microfluidic device comprising: wall structures comprised of
sintered glass frit; a glass, glass-ceramic or ceramic membrane
structure sealed by a sintered seal to said wall structures; a
fluid passage or chamber defined at least in part by said wall
structures and said membrane structure, said membrane structure
being deflectable by changes in pressure within the fluid passage
or chamber.
2. The device according to claim 1 further comprising at least one
planar substrate structure sealed to said wall structures by a
sintered seal, the planar substrate structure being thicker than
the membrane structure, the passage or chamber being defined by the
planar substrate structure and the wall structures and the membrane
structure.
3. The device according to claim 1, further comprising one or more
floor structures formed of sintered glass frit and wherein the
passage or chamber is defined by the planar substrate structure and
the wall structures and at least one of the one or more floor
structures.
4. The device according to claim 1 further comprising multiple
fluid passages or chambers each defined at least in part by said
wall structures and by a respective area of said membrane
structure, whereby changes in pressure within each respective fluid
passage or chamber cause deflections of respective areas of the
membrane structure.
5. The device according to claim 1 further comprising an electrode
of a capacitor structure disposed on the surface of the membrane
whereby deflections of the membrane may be detected as changes in
the capacitance of the capacitor structure.
6. The according to claim 1 further comprising an optical element
disposed on the surface of the membrane whereby deflections of the
membrane may be detected optically due to motion of the optical
element.
7. The device according to claim 6 wherein the optical element
comprises a grating.
8. The device according to claim 6 wherein the optical element
comprises a reflector.
9. The device according to any of claim 1 further comprising a
strain gauge structure disposed on the surface of the membrane
whereby deflections of the membrane may be detected via the strain
gauge.
10. A method for producing an integrated pressure sensor in a
sintered-glass-frit-containing microfluidic device, the method
comprising: providing a flexible glass, glass-ceramic or ceramic
membrane; forming microfluidic chamber or passage wall structures
defining at least one chamber or passage in which pressure is to be
sensed, the wall structures comprising a glass frit; sintering the
wall structures while the wall structures are in contact with the
membrane such that resulting sintered walls form a seal with the
membrane, and the membrane forms a boundary of the at least one
chamber or passage.
Description
[0001] This application claims priority to U.S. provisional
application No. 60/755,601 filed Dec. 31, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to pressure sensing
devices integrated into glass, glass-ceramic, or ceramic
microreactor fluidic structures for use in chemical processing, and
particularly to glass microreactor pressure sensors that are
fabricated using glass, glass-ceramic, or ceramic sheets and glass
frit (i.e., glass powder).
[0004] 2. Technical Background
[0005] Microreactor-type chemical processing units have been
proposed where fluids (liquids or gases) are guided in etched,
molded, drilled or otherwise formed fluid channels in or on planar
substrates. Fluid channels are patterned with elementary fluidic
structures (e.g., mixers and residence time segments) to form
circuits that provide more complex chemical processing functions.
Planar substrates can be stacked to extend functionality in a
single reaction unit, providing a modular chemical processing
system that can target multiple applications.
[0006] Because of its transparency, chemical and physical
durability, biological and chemical inertness, tolerance of extreme
temperatures and other properties, glass is an attractive material
for use in such microreactor devices. In using microreactors and
similar microfluidic devices, it is desirable to be able to detect
the internal pressure at key points within the device or at key
points within the process performed in the device. Chemical
processing systems, for example, often require active monitoring of
fluid pressures for process control and safety monitoring
functions. A sudden change in operating pressure could indicate an
abnormal processing condition or a leak in the reactor device.
[0007] However, the very properties of chemical and physical
durability that make glass materials desirable also make them
difficult to form into complex structures. A simple way to form
microreactor and other microfluidic structures in glass, with
provision for integrated in situ pressure sensing, is thus
desirable.
SUMMARY OF THE INVENTION
[0008] The present invention includes among its embodiments
integrated pressure sensors in glass-frit based microfluidic
devices, as well as methods for producing integrated pressure
sensors in a glass-frit based microfluidic devices. According to
one embodiment, the method includes providing a flexible glass,
glass-ceramic or ceramic membrane, and forming out of glass frit
wall structures that define, at least in part, at least one
microfluidic chamber or passage in which pressure is to be sensed,
and sintering the wall structures while the wall structures are in
contact with the membrane such that resulting sintered walls form a
seal with the membrane such that the membrane forms a boundary of
the at least one chamber or passage.
[0009] The step of forming wall structures may further include
forming wall structures upon a substrate other than said membrane.
This other substrate may be, but is not required to be, a glass
substrate. This other substrate may also be a ceramic or a
glass-ceramic substrate, for example. The step of forming wall
structures may alternatively or in addition include forming wall
structures directly upon the membrane.
[0010] As another alternative, glass frit based floor structures
may also be formed, and may form a boundary of the chamber or
passage opposite the membrane.
[0011] As yet another variation of this embodiment of the inventive
method, the step of forming microfluidic chamber or passage wall
structures may include defining multiple chambers or passages in
which pressure is to be sensed. If desired, the same membrane may
be used to form a boundary of the multiple chambers or
passages.
[0012] The wall structures may be formed as both thin and thick
wall structures, and the membrane may be sintered and sealed only
to the thin wall structures, if desired. This is one way in which
the membrane may be located internally in the device, as is
explained in the detailed description below.
[0013] Another aspect of the present invention relates to a
microfluidic device having wall structures comprised of sintered
glass frit and a glass, glass-ceramic or ceramic membrane structure
sealed by a sintered seal to said wall structures, such that a
fluid passage or chamber is defined at least in part by the wall
structures and said membrane structure. This allows for changes in
pressure within the fluid passage or chamber to cause deflections
of the membrane structure, providing for direct measurement of
pressure within the device. The microfluidic device may have both
floors and walls of sintered frit, or may have only walls of
sintered frit, with planar floor-like substrate structures, thicker
than the membrane structure defining the vertical boundaries of the
internal passages. The device may include multiple fluid passages
or chambers each defined at least in part by a membrane structure.
Multiple membrane structures may be used in a single device, and
one single membrane structure may be used for multiple passages or
chambers.
[0014] Deflection of the deflectable areas of the membrane or
membranes in a given device may be accomplished by capacitive or
optical detection, or by a strain gauge, or other suitable
means.
[0015] Additional features and advantages of various embodiments of
the invention will be set forth in the detailed description which
follows, and in part will be readily apparent to those skilled in
the art from that description or recognized by practicing the
invention as described herein, including the detailed description
which follows, the claims, as well as the appended drawings.
[0016] It is to be understood that both the foregoing general
description and the following detailed description present
embodiments of the invention, and are intended to provide an
overview or framework for understanding the nature and character of
the invention as it is claimed. The accompanying drawings are
included to provide a further understanding of the invention, and
are incorporated into and constitute a part of this specification.
The drawings illustrate various embodiments of the invention and
together with the description serve to explain the principles and
operations of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a flow diagram of one embodiment of a process of
the present invention;
[0018] FIG. 2 is a cross-sectional view of a microfluidic device
according to an embodiment of the present invention;
[0019] FIG. 3 is a cross-sectional view of a microfluidic device
according to another embodiment of the present invention;
[0020] FIG. 4 is a partial perspective view of another embodiment
of a device, partially assembled, according to the present
invention;
[0021] FIG. 5 is the a cross-sectional view of a device according
to yet another embodiment of the present invention;
[0022] FIG. 6 is a graph of deformation, as a function of pressure,
of membranes of a type useful in the context of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Reference will now be made in detail to the present
preferred embodiment(s) of the invention, examples of which are
illustrated in the accompanying drawings. Whenever possible, the
same reference numerals will be used throughout the drawings to
refer to the same or like parts. One embodiment of a method of the
present invention is shown in FIG. 1, and is designated by the
reference numeral 10. The method 10 illustrated in FIG. 1
constitutes the basic steps of an embodiment of a method for
producing an integrated pressure sensor in a glass-frit based
microfluidic device.
[0024] The method includes step 20, providing a flexible glass,
glass-ceramic or ceramic membrane. Glass may be preferred for its
transparency, but transparency is not a requirement. Strength and a
degree of flexibility are more important. The method also includes
step 22, forming microfluidic wall structures defining at least one
chamber or passage in which pressure is to be sensed, the wall
structures comprising glass frit. The wall structures comprising a
glass frit may be formed by press-molding, injection molding,
thermo-forming or other techniques or combinations of these forming
methods, typically employing an organic binder to allow the frit to
be formed. Forming methods employing frit allow the formation of
relatively complex structures as an up-building process rather than
as a subtractive process which can be difficult and expensive in
glass materials. The wall structures may be molded or otherwise
formed integrally with their own floor structure or on a substrate
such as a glass, glass-ceramic or ceramic substrate. Alternatively,
the wall structures may be molded or otherwise formed directly onto
the membrane. However formed, the frit wall structures are placed
in contact (if not already in contact) with the membrane and
sintered in step 24. Step 24 is sintering the wall structures while
the wall structures are in contact with the membrane such that
resulting sintered walls form a seal with the membrane. This
results in the membrane forming a deformable boundary of a fluidic
chamber or passage within the microfluidic device, and displacement
of the membrane is then used to measure pressure or pressure
variation within the microfluidic device.
[0025] FIG. 2 is a cross-sectional view of an embodiment of
microfluidic device 30 according to the present invention. In this
embodiment, frit walls 34 have been formed on glass substrates 36.
Fluid passages 37 are defined by the walls 34 and the substrates
36. A glass membrane 32 has been placed in contact with the frit
walls 34 on the top of the substrate 36 uppermost in the figure. A
fluid chamber 35 or fluid passage 37 is defined by the membrane 32,
particularly by the deformable portion 39 thereof, together with
the associated frit walls 34 and substrate 36. A through-hole 38
through the associated substrate 36 provides access to the chamber
35 or fluid passage 37. Although this embodiment and other
embodiments of the invention will work with a fluid chamber 35
(i.e., with a dead-end chamber 35 having no flow through it during
normal microfluidic device operation), it is generally preferred to
use a fluid passage 37 (with flow, for example, in the direction
into the plane of the figure) rather than a dead-end chamber, as a
means of reducing the chances of fouling. The state of the device
as shown in FIG. 1 may be understood as just before sintering. The
sintering step then serves to seal or fuse each of the frit walls
with the adjacent substrate or membrane material. Thus the pressure
sensor is formed by sealing to the frit walls 34 simultaneously
with the rest of the fluid passages 37 of the microfluidic
device.
[0026] FIG. 3 shows an embodiment similar but alternative to that
of FIG. 2. In the embodiment of FIG. 3, no substrates 36 are
present. Instead, the wall structures 34 have been formed of frit
material integrally with floor structures 33 formed of the same
frit material. Thus the desired structures can be formed without
the potential limitations imposed by the use of substrates, such as
the potential difficulty of providing through-holes. Though-hole 38
of FIG. 3 need only be molded into the frit material forming the
floor structures 33. The embodiment of FIG. 3 also differs from
that of FIG. 2 in that first and second chambers 35a and 35b are
both sealed by the membrane 32. Thus multiple sensors may be
provided for in a single device, and even with a single membrane
32. Of course multiple membranes may be used if desired.
[0027] FIG. 4 shows a perspective view of a portion of another
device according to the present invention. FIG. 4 shows a substrate
36 with a layer of frit wall material disposed on it. The frit
walls define three differently shaped chambers or passages 35a,
35b, and 35c. A membrane has not yet been brought into contact with
the frit walls of FIG. 4, so that shapes and profiles of the
various alternative chambers 35 may be readily seen.
[0028] FIG. 5 is a cross-sectional view of a device according to
yet another embodiment of the present invention. In the device of
FIG. 5, substrates 36 protect the outermost portions of the device
(in the up and down direction in the figure). In addition to the
normal-height frit walls 34, the device includes thin or short frit
walls 44, upon which a membrane 32 is positioned between the
outermost substrates. Membrane 32 is provided with fluid (and fluid
pressure) through through-hole 38. The basic structure for
capacitive pressure sensing is also provided in the embodiment of
FIG. 5. One electrode in the form of a layer of conductive material
52 is disposed on the membrane 32. A second electrode in the form
of a conductive layer 50 is disposed nearby on the underside of the
uppermost of the substrates 30 in the figure, and extends rightward
to a contact point 56. From contact point 56 the capacitance of the
capacitor formed by layers 50 and 52, and the intervening air gap
54, may be measured, thus allowing deformation of the membrane 32
to be measured, and the associated pressure to be measured.
[0029] Alternatives to the capacitive detection of deflection of
membrane 32 include optical detection such as with interferometric
detection using a mirrored surface or other optically detectable
surface disposed on the membrane in place of conductive layer 52.
As another alternative, a strain gauge may be disposed on the
membrane in place of conductive layer 52.
Experimental
[0030] Experiments on glass diaphragm deformation under applied
pressure were performed. Thin glass diaphragms with thicknesses of
0.186 and 0.7 mm were clamped in a pressure testing fixture and
restrained to create an 8 mm diameter circular diaphragm. Pressures
of up to 4 bars were applied to the diaphragms, with diaphragm
deformation measured during pressurization via surface
interferometry. Results are plotted in the graph of FIG. 6. Error
boxes around data points indicate measurement uncertainty due to
pressure gauge reading and surface interferometry diaphragm edge
determination. The results show relatively good linearity over a
relatively wide pressure range.
[0031] Embodiments described above enable integration of pressure
sensing in an all-glass or all glass, ceramic, and/or glass-ceramic
or related type microreactor while adding no additional, or at
least a minimum of additional process steps, and while preserving,
if desired, an all-glass environment within the fluidic channels or
chambers. Such integration may be used to avoid the need for
external sensors with the typical resulting proliferation of
fluidic connections and dead volumes, and may be used to provide a
way to directly detect pressure and/or other important properties
of the internal microfluidic environment. The pressure sensors of
the present invention may be applied, in combination with each
other or with other sensors, to detect mass flow rates, for
example.
[0032] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. Thus
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *